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Re: GPS Requires Network??

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On 3/29/2011 3:42 AM, Patricia Shanahan wrote:
> On 3/28/2011 3:26 PM, Lawrence D'Oliveiro wrote:
>> In message<slrnip0t5n.rs9.bcd@decibel.pvv.ntnu.no>, Bent C Dalager wrote:
>>
>>> On 2011-03-28, Lawrence D'Oliveiro<ldo@geek-central.gen.new_zealand>
>>> wrote:
>>>
>>>> Why would GPS require a network connection?
>>>
>>> If LocationProvider provides both fine grain and coarse grain
>>> localisation services, then it uses GPS for the fine grain
>>> localisation which obviously requires access to the satellite
>>> receiver; and it reads nearby WiFi SSIDs to calculate coarse grain
>>> localisation which requires access to the WiFi radio.
>>
>> There is a separate LocationProvider called “network”, that says it
>> requires
>> both a cellular network (requiresCell()) and data network
>> (requiresNetwork()). That provides lower accuracy than GPS, so there’s no
>> reason for the GPS provider to do the coarse-grained stuff as well.
>>
>
> Maybe it is using the network LocationProvider as a back-up for
> situations, such as inside many buildings, in which GPS does not work
> but cell and WiFi are available.

Incidentally, this is a testable hypothesis. The test would consist of
taking the device into a building or parking structure, with a few
layers of reinforced concrete between the device and the sky, and asking
the GPS provider for a location.

If the hypothesis is correct there will be cases in which it reports
insufficient satellites for a GPS fix, but gives a location.

If the hypothesis is incorrect, it will fail to report a location if it
has insufficient GPS satellites, even if there is cell phone and WiFi
coverage.

Patricia

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Re: GPS Requires Network?? Patricia Shanahan <pats@acm.org> - 2011-03-29 08:52 -0700

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